eddison, I think what many will say is that you have to figure out what to do and make the choice. The first time I found something like that, I left. I packed up the cat and waddled out the door (9 months pregnant.)
It wasn't ok with me. I didn't want to be around the stuff. I didn't want a baby to be around the stuff. You hear in the news all the time about some infant/toddler who got a'hold of something and ended up in the hospital.
If he was (as far as you knew) trying to get off the vicodin and that was the understanding, then he broke his word. Even if it wasn't 100% out there and agreed upon, it's still bad news.
You need to decide what you are OK with, what you are not OK with and lay it all out. He probably has something to say about it. I think many addicts would deny. "It's not mine." "I hadn't used it yet." "It's old stuff." My rule now is that if I find it, he was intending to use it and no amount of denying will ever change that. Addicts lie. They lie to save face, or for whatever other reason you can think of.
Were I in your shoes, I'd throw it out, all of it. I'd tell him what I found and that he broke his word. I'd tell him I think he's an addict and it's not tolerated in a house with a child. If he rages and rails, then I'd take my child and go quietly. But, I'm a "no nonsense/no tolerance" kind of person and he knows this.
My instinct for protecting my baby and protecting myself far outweighs what I think might happen if I leave.
Whatever you do, just try to stay calm and remember, the chance that he will lie or deny are very good. You found the stuff. He's using. You know that. All the pretty words and promises, well . . . you have to consider them meaningless at this point. That's my two cents. You may feel differently and want to react differently. Go with your gut. Just try to keep things calm, especially if there is a child in the house.